§ 6. A minute comparison of the megarhine teeth with those of the living species of Rhinoceros proves the truth of Professor Owen's* remark, that each recent species may be identified with absolute certainty by one isolated upper molar. In the fossil species. also the maximum amount of specific variation is to be found also in the upper molar series. Choosing the salient characters of the megarhine teeth, we find remarkable points both of agreement and difference. 1. The accessory valley. The anterior combing plate meeting the posterior insulates the accessory from the anterior valley in the +Unicorn Rhinoceros of India, the R. simus (Burchell's Rhinoceros) of South Africa; and in R. bicornis, true molars one and two being excepted; while in the R. Sumatranus and R. Javanus the anterior combing plate is undeveloped, and therefore there is no accessory valley defined, as in the leptorhine and megarhine species. 2. The Colles. The anterior and middle colles taper from the base towards the summit of crown; and the latter of them is slightly hooked, in the bicorn African, bicorn Sumatran, and * Odontography, Article Rhinoceros. † Fischer (tom. cit. p. 414 et seq.) and Van der Hoeven (Handbook of Zoology, Vol. ii.) give the synonymy of the various living species of Rhinoceros, to which reference can be made. The names used in the text are those of the catalogues of the Hunterian and British Museums. Unicorn Javan species. The third collis is notched and cuspless in R. Javanus, and R. bicornis of Sennaar: all of which are points of agreement. In the Sumatran species, on the other hand, the third Collis bears a cusp, as in the tichorhine Rhinoceros. 3. The guard. The R. unicornis of India, R. Javanus, R. bicornis and R. Sumatranus, bear a strongly defined guard on their anterior aspect as in the megarhine species. 4. The external lamina. In the four last-named species, as in the megarhine, the second costa of the external lamina, in R. simus on the other hand and R. tichorhinus the first, is the higher. In fine, the dentition of the megarhine species presents a combination of characters now scattered among widely-isolated species of the same genus. The curious problem as to how the characters of the extinct became shared among the living species, and how others, not found in the former, were superinduced in the latter, is, to my mind at least, incapable of any other solution than that offered by Mr. Charles Darwin's "Theory of descent with modification." The unicorn R. Javanus, and the bicorn R. Sumatranus approach more closely to the extinct bicorn R. megarhinus than any other living species. 9. Right upper molar series, except Premolar one, crown surface, }. 14. Right lower molar series, except premolar one, inner surface, . 15. Right lower molar two, external surface, nat. size. XXXV.-ON PORTIONS OF A CRANIUM AND OF A JAW, IN THE SLAB CONTAINING THE FOSSIL REMAINS OF THE ARCHEOPTERYX. By John Evans, F.R.S., F.G.S. Ir will be remembered that in the admirable and exhaustive account of the slab containing the unique remains of the Archæopteryx lithographica of Von Meyer (A. macrura, Owen) read before the Royal Society in November, 1862, by Professor Owen, it was stated that beside some other less important portions of the skeleton, the head of that marvellous bird was wanting on the stone; and it was suggested that as the front margin of the slab had been broken away short of the anterior border of the impression of the outspread left wing, the head or skull of the specimen might have been included in that part of the quarry or stone from which the slab had been detached. But upon a careful examination of the slab made on two separate occasions soon after the reading of that paper, I discovered two objects which appeared to have escaped Professor Owen's notice, one of which I thought might with safety be referred to the head of the Archeopteryx, and the other, though of much more doubtful attribution, might possibly belong to it also. I at once brought this discovery under the notice of Professor Owen, and on the publication of his paper in the Philosophical Transactions for 1863, he called attention to the subject by engraving the objects in the margin of the plate of the slab containing the Archeopteryx remains, and also appended the following succinct remarks in his explanation of the plate. n. Concretionary nodules: the larger one consists of matrix, which filled a cavity, n', formed by a thin layer of brownish and crystalline matter; which may be, as suggested by Mr. John Evans, F.G.S., part of the cranium with the cast of the brain of the Archeopteryx. n' Cavity with a layer of brown matter, in the counterpart of slab, which was applied to the nodule n'. Fig. 3. p'. Premaxillary bone, and Fig. 1 p, its impression, resembling that of a fossil fish. Professor Owen has also engraved for comparison, a cast of the fore-part of the brain-cavity of a magpie which I left with him, but has abstained from offering any decided opinion as to the correctness of my attribution of the corresponding object on the slab to the head of the Archæopteryx. As some time has now elapsed, and I have seen no reason to make any change in my views, I venture to bring the subject again before the public. The fossil bird, as is well known, is preserved on two slabs of the Solenhofen lithographic stone. One of these, containing the principal bones and the clearest impressions of the feathers, I shall speak of as the principal slab; and the other, which though containing but few of the bones, is still of the utmost importance for completing our knowledge of the character of the fossil, I shall term the counterpart. On the principal slab, between the posterior margin of the right wings and the lower extremity of the right tibia of the bird, is a rounded protuberance, in general outline forming a crescent, with a depression in the centre of its convex side, dividing it into two lobes. On the concave side of the crescent, the limestone of the slab rises to a higher level than it does on the convex side, so that the outline of the lobes is not so well defined on that side, and the upper portion of one of them has moreover been broken off together with a portion of the matrix. Around the margin of the crescent-shaped protuberance may be discerned a section of a thin film of sparry matter, representing the place where bone has been, which is continued on in a curved line beyond the outer end of the more perfect lobe, forming as it were a long thin horn of the crescent. The counterpart does not exactly correspond with the principal slab, as a portion of the matrix has been chipped away from the latter since the block was split, causing the injury to one of the lobes, which I have already mentioned; but in it, is a crescent-shaped portion of the sparry layer which takes the place of bone in the slab, showing the two concavities in which the rounded lobes on the principal slab were moulded, with a projecting ridge between them. There can, I think, be but little hesitation in recognizing in this crescent-shaped object, a portion of the anterior part of the missing cranium of the Archeopteryx, while on the slab itself is a cast of a portion of the brain-cavity, showing distinctly the two hemispheres of the brain and the median line, corresponding with the intercerebral ridge, which is so plainly visible on the counterpart. Indeed, so evidently is this the case, that Mr. Carter Blake recognises upon the cast of the brain "the site of the olfactory lobes," and perhaps "some trace of the optic lobe beneath the brain." *Geologist, Vol. vi. p. 7. To those who have carefully examined the fossil, it may seem superfluous to attempt to prove that these remains are really organic; but as I understand that some doubts have been expressed upon this point, I would call attention to the following facts 1st. That the presence of a layer of calcareous spar of exactly the same character as that which distinguishes the bones upon the slab is evident around the bilobed projection on the principal slab, and the mould in the counterpart in which they were formed is a continuation of the same sparry layer. 2ndly. That assuming this sparry layer to represent the former existence of bone, as to my mind it undoubtedly does, there is no bone which presents an analogous bilobed cavity with the exception of the skull; and 3rdly. That the position of the remains refers them to the Archaeopteryx, while the ornithic character of the cast of the brain cavity is in perfect accordance with the other portions of the skeleton of this curious creature. I therefore regard the evidence on which rests the attribution of this part of the fossil to the head of the Archæopteryx as sufficiently conclusive to justify some further speculation upon the subject. I would, however, rather leave this to others better versed in anatomy, and will only venture upon a single suggestion with regard to the position of the brain in relation to the beak. Although from the nature of the matrix in which the skull was imbedded, there has probably been some compression and distortion of its form, yet these appear to have been but slight and not sufficient to affect in any material degree the shape of the interior cavity, of a portion of which we have here a cast in indurated mud. For the sake of comparison I have made plaster casts of the brain-cavities of a number of birds belonging to different orders; and though I find a considerable range in the proportion of the brain-cavity to the other parts of the skull, and also in the character and extent of the intercerebral ridge, yet the general resemblance of the anterior portion of the brain of all the birds which I have examined to that of the Archæopteryx is most distinct. The casts of the interior of the forepart of the skulls of the Jay and the Woodcock (Garrulus glandarius and Scolopax rusticola) more particularly exemplify this resemblance. We may from this and from the presence of feathers (as was so well pointed out by Professor Owen), infer that the Archæopteryx was provided with a beak more or less analogous in character with that of other birds. N.H.R.-1865. 2 F |